Backcountry snowboarding appeals to riders who wish to ride untracked snow, avoid the crowds of commercial resorts, and spurn limitations on what and where they can ride. There are no ski-lifts in the backcountry, so the snowboarder must climb the slopes by physical effort. Some snowboarders simply carry their board and hike up, but progress can be almost impossible if the hiker sinks deep in soft snow. Travel efficiency can be improved with snowshoes, but the rider must still find a way to carry their board up the slope.
Saving effort is the name of the game in the backcountry; it determines how many runs a rider is going to make in a day. If riders are exhausted by the time they reach the top of the run, they aren't going to snowboard to the best of their ability, or enjoy themselves as much as they could.
Splitboards are a recent improvement. When assembled, a splitboard looks like a snowboard, but can be taken apart to form a pair of skis. The right and left “skis” of a splitboard are asymmetrical; i.e., they are the mirror halves of a snowboard—longitudinally cut (or “split”), and typically have the sidecut (ie. nonlinear long edges) and camber of snowboards.
When touring cross-country and uphill to reach the slopes, the skis are worn separately. Cross-country travel on skis requires less effort than hiking or snowshoeing. Since the rider is wearing the skis instead of carrying a snowboard, the effort is less tiring—the rider can glide along, and there is no extra weight to carry up the slope. The wider track of the splitboard skis reduces sinking in soft powder snow.
“Free heel” ski bindings and adaptors, such as telemark, randonee or Alpine Trekkers, make ski touring easier. In addition, the skis may be adapted for climbing by applying climbing skins to the lower surface of the skis. The use of climbing bars propped under the boot heels aids in climbing steeper slopes and crampons may be used in icy conditions to decrease the risk of slipping. Free heel bindings, climbing skins, climbing bars and crampons are used by touring splitboarders as well.
In the occasional descent in ski touring mode, the heels of the boot bindings are optionally “locked down” to the skis, with descent using conventional alpine techniques, or more commonly left free with the toe attached by a pivot, with descent using telemark ski techniques.
The splitboard reveals its true utility on the downhill rides. The rider first joins the two skis of the split board pair to form a snowboard-like combination. The rider's stance in the snowboard riding configuration is sideways on the board, with legs spread for balance. Ideally, the rider descends the slope as if riding a snowboard, with heels and toes locked in place.
Some boards, known as “swallowtails”, are designed for deep powder snow. These boards have forked tails that allow the tail of the board to carve more deeply in the snow while keeping the nose of the board high.
Another version of splitboards, recently innovated in Europe, is formed with two narrow skis and a third fitted plank between the skis. When ski touring, the extra plank must be carried. It remains to be seen whether this will catch on in backcountry snowboarding elsewhere.
It should be noted that downhill skiing and snowboard riding require very different styles and skills. With skis, the body points in the same direction as the skis, and the skier uses hips and knees to change direction. Knee injuries are common because the legs move separately. On a snowboard, the body is essentially crossways on the board, and both heels are firmly attached to the board so that the feet, ankles, hips, and upper body can be used to set the board on an edge and make a turn. Knees are more protected because both legs are firmly secured to the board.
Backcountry splitboarding, which combines ski touring and snowboarding, thus requires boot bindings adaptable for both ski configuration (ie. one to a ski) and for snowboard configuration, (ie. joining the skis as a snowboard).
In one widely used configuration of the prior art, mounting block assemblies are attached in pairs crosswise on the opposing ski member halves of the splitboard, one pair for the forward leg and one pair for the back leg. These mounting blocks, disclosed in U.S. Pat. No. 5,984,324 to Wariakois (hereby incorporated in full by reference) include a toe mounting block and a heel mounting block, which are designed to slidingly receive an adaptor mounting plate (see the C-channel, item 74 of FIG. 6 of U.S. Pat. No. 5,984,324, also termed “slider plate”) and attached upper binding baseplate (item 72 of FIG. 6 of U.S. Pat. No. 5,984,324, also termed the “boot mounting assembly”), thereby conjoining the two ski members to form a snowboard. The mounting blocks, made of filled (fiber reinforced) nylon, are inherently compliant, and no means for dampening the compliance of the mounting blocks and associated stack of parts of the bindings is suggested. The adaptor mounting plate is also narrow relative to the width of the boot support plate as shown in FIG. 5 of U.S. Pat. No. 5,984,324. The narrowness of the C-channel saves weight, but reduces stability. Nonetheless, the adaptor mounting plate alone adds about 7 oz (or 200 g) of weight to each boot, and the total weight of an adaptor mounting plate with attached upper binding baseplate and bindings can be 1.5 kg or more per foot, dramatically increasing the rider's burden. A rear stop tab on the adaptor mounting plate prevents the plates from sliding forward over the heel mounting block and a clevis pin is used to lock the toe of the adaptor mounting plate on the toe mounting block.
This same clevis pin is used as a pivot pin when the adaptor mounting plate is relocated to a ski mounting bracket. But experience has shown that the forces on the pivot pin are such that the pivot pin cradle and adaptor mounting plate of the prior art rapidly fatigue and are ovally deformed, leading to heel “fishtailing” in free heel mode, which destabilizes the rider and which must be repaired by replacement of the worn parts.
A second system for grippingly conjoining the ski member halves of a splitboard is disclosed in U.S. Pat. No. 6,523,851 to Maravetz, hereby incorporated in full by reference. This system employs a recessed ring with raised flanges that mate with a clamshell adaptor plate to secure the upper boot assembly to the board. The preset angle of the foot relative to the board can be changed by use of a locking pin in the rotatable lower half of the lower adaptor plate. The clamshell is hinged at the toe, but conversion from touring mode to snowboard mode can be difficult with this system because snow often gets inside the clamshell works during touring, and consequently this system has proved less than satisfactory in field experience by snowboard riders.
Both of the above prior art splitboard systems employ stacked mechanical members, including interposed adaptors, to secure the boot bindings to the board interchangeably between ski and snowboard configurations. In addition to the ski member conjoining function, these approaches teach the utility of a universal mounting system and upper binding baseplate for the industry-standard (3- or 4-hole) disk used in most strap-type or step-in snowboard and ski boot mounting systems, including for hard, hybrid, or soft boots. An even more complex example of an adaptor plate is shown in US 20040070176 to Miller. These teachings point to the continued need for improvement in this field.
Splitboarding is no longer a crossover sport. The majority of board riders have developed a preference for soft boots, which many find to be lighter, more comfortable, and better adapted to the style of riding they prefer. Only a minority of riders use hard boots. Board riders typically require a greater range of motion at the ankle than hard boots provide. Flexibility at the ankle (also known as “foot roll”) enhances the rider's ability to shift his or her weight and body position around the board for balance and control by allowing for a wider range of angles the legs can make with the board. For example in riding over a mogul, the rider shifts weight to the back of the board as the angle of the slope changes, or in carving a turn in hard snow, the rider will lean forward on the board. Flexibility may also improve the overall ride by allowing bumps to be more readily absorbed by the ankles and knees. Thus, the freedom of the foot to “roll”, and allow the angle of the leg to change relative to the board provides a performance and feel that many riders find desirable. Soft boots have emerged as a clear preference among splitboarders.
Boot bindings for use with soft boots are of two basic types: “strap bindings” and “step-in bindings”. A strap binding, which has been the traditional type of binding for a soft boot, includes one or more straps that are tightened across various portions of the boot, securing the boot in a boot pocket formed by the binding upper. For example, an ankle strap may be provided to hold down a rider's heel in the heel cup and a toe strap may be provided to hold the front portion of the rider's foot.
Step-in snowboard bindings, both toe-and-heel and sole side-grip bindings, have been developed for use with soft snowboard boots. Most of these require specially fabricated boots matched to the bindings. “Bails” may be used at the heel or toe to secure the boots, as with mountaineering boots. Newer innovations include highbacks with click locking mechanisms.
However, while innovation continues, the prior art has not produced a boot binding optimized for splitboarding. Components of the prior art—including 4-hole disk bindings, adaptor mounting plates, slider tracks, rubber gaskets, and filled-nylon upper binding baseplates, for example—increase overall wobble experienced by the rider (due to additive stacked tolerances and compliances), add weight, and put more height between the rider's heel and the board itself: all undesirable characteristics. The lack of firm broad contact between the most commonly sold adaptor mounting plate and the board surface also adds to the rider's instability.
The added “flex” or “play” in the mechanics of the prior art adaptor mounting plates, and associated mechanical stack members, which float above the surface of the board (see Example 2), results paradoxically in dampening of the rider's movements with respect to the board and loss of control. The apparent paradox arises because although freedom of movement of the ankle in the boot binding is essential to good riding, there must also be torsional stiffness—the rider's motions must be resisted by an optimal level of stiffness in the binding so that the legs cannot simply flop back and forth, but rather the binding resists this torsional motion (in the engineering sense) with a spring-like stiffness, allowing the rider to apply pressure at the desired segment along the length of the board.
The board is controlled by the bite of its edges in the snow. The rider steers by relocating pressure from one side of the board to the other as well as from nose to tail. Toeside and heelside turns on a snowboard involve a complex combination of dorsiflexion and plantar flexion, plus the roll of the calcaneus, talus, and subtalar joint, nosewise and tailwise on the board. While these motions would seem to be favored by a completely loose binding, in fact, an optimal torsional binding stiffness is required. Torsional stiffness is the spring force in the bindings that opposes the rider's motion. This opposing force translates the rider's motion into pressure on the desired section of the board. When the rider bends downslope, for example, the boot bindings transmit pressure onto the nose of the board. When the rider bends upslope, the boot bindings transmit pressure onto the tail of the board. Similar forces come into play as the rider leans toeside or heelside. If the bindings lack torsional stiffness, the ability to apply control pressure to the intended segment of the board is decreased. Torsional looseness is felt as “play”, “slop” and instability. Conversely, if the bindings are too stiff, the legs cannot pivot, and the rider loses balance and control. Therefore, there is an optimal stiffness, providing an optimal mix of freedom of motion and board control.
While hard ski boot bindings are too stiff to allow the range of motion most snowboarders prefer, the splitboard systems of the prior art incorporate a soft boot binding with an adaptor mounting plate that is not stiff enough and has excess play. Although the rider can readily bend at the ankle, the lack of stiffness prevents the rider from precisely transmitting that force as a directed pressure at the desired segment of the board.
A problem first recognized and addressed by this invention is thus one of enhancing the torsional stiffness of snowboard boot bindings for use with splitboards in “snowboard riding mode”, and simultaneously improving performance and comfort of the equipment in free-heel “ski touring mode”. There is an unmet need for splitboard soft boot bindings with the stiffness, weight, and heel height for today's splitboard riding styles. This need necessitates a mechanical reinvention of the boot bindings from the board up.